Portable derricks



March 26, 1957 R. o. BALOGH 2,786,531

PORTABLE DERRICKS Original Filed June 10, 1955 5 SheetS -Sheet 1INVENTOR.

ROY o. BALOGH f m MMzt ft ATTORNEY March 26, 1957 O, BALOGH 2,786,581

PORTABLE DERRICKS Original Filed June 10; 1955 5 Sheets-Sheet 2INVENTOR.

ROY O. BALOGH ATTORNEY March 1957 R. o. BALOGH PORTABLE DERRICKS 3Sheets-Sheet 3 Original Filed June 10, 1955 u lm IN V EN TOR.

ROY O. BALOGH United States Patent PORTABLE DERRICKS Roy 0. Balogh,Clayton, Mo., assignor to McCabe-Powers Auto Body Co., St. Louis, Mo., acorporation of Missoun Contilguation of application Serial No. 514,462,June 10,

19 Claims. (Cl. 212-8) This invention relates in general to certain newand useful improvements in portable derricks and, more particularly, toa vehicle-mounted derrick adapted for movement from a horizontal orso-called transport position to various upright or work positionsthrough an arc in excess of 180. This application is a continuation ofmy copending application Serial No. 514,462, filed June 10, 1955.

Service and maintenance trucks employed by public utilities and similarcompanies are ordinarily provided with some type of derrick which can beused in lifting equipment up and down, setting poles, removing worn outor defective poles and replacing them, and similar types of work. Suchderricks are usually pivoted near the rear end of the truck body andextend forwardly in a substantially horizontal position over the top ofthe body when the truck is moving from place to place. This position isusually referred to as the transport position. For actual use, thederrick is elevated into various upwardly and rearwardly inclinedpositions usually referred to as work positions. However, many types ofwork encountered in the field, such as the lifting of heavy equipmentfrom the truck body to the ground and then elevating it to the pole,necessitates swinging the derrick downward-1y over the rear end of thetruck to a rearwardly extending horizontal position or even, in somecases, a rearwardly and downwardly inclined position. Thus, the derrickmust swing through an arc in excess of 180 during these work-operations.Considerable difficulty in this respect is encountered with conventionaltypes of portable deiricks by reason of the fact that conventionalderricks cannot swing more than 180 and, in fact, many conventionalderricks have an even more limited arc of movement.

It is, therefore, the primary object of the present invention to providea power operated vehicle-mounted or portable derrick which can be swungfrom inoperative transport position to upright or work-position quickly,efficiently, and is capable of swinging through an are substantiallygreater than 180.

It is also an object of the present invention to provide avehicle-mounted derrick of the type stated which, when in operativeposition, can be swung forwardly and rearwardly by power driven meansand is thus capable of reaching various desired positions outwardly anddownwardly to the rear of the truck body on which it is mounted.

it is a further object of the present invention to provide a portablederrick of the type stated which can be manipulated to and fromtransport position and into various operative positions by a singleoperator and is capable of a wider range of movement than conventionaltypes of portable derricks.

With the above and other objects in view, my invention resides in thenovel features of form, construction, arrangement, and combination ofparts presently described and pointed out in the claims.

This application May 7, 1956, Serial No.

Patented Mar. 26, 1957 In the accompanying drawings (three sheets)Figure 1 is a side elevational view of a utility maintenance truckequipped with a portable derrick constructed in accordance with andembodying the present invention;

Figure 2 is a diagrammatic view of the hydraulic system forming a partof the present invention;

Figure 3 is a fragmentary top plan view of the utility maintenance truckequipped with a portable derrick constructed in accordance with andembodying the present invention;

Figure 4 is a fragmentary side elevational view showing the derrick inupright or work-position;

Figures 5 and 6 are fragmentary sectional views taken along lines 55 and6--6, respectively of Figure 1;

Figure 7 is a fragmentary perspective view of a modified form ofportable derrick constructed in accordance with and embodying thepresent invention; and

Figure 8 is a fragmentary perspective view of a further modified form ofportable derrick constructed in accordance with and embodying thepresent invention.

Referring now in more detail and by reference characters to thedrawings, which illustrate practical embodiments of the presentinvention, A designates a utility maintenance truck equipped with aso-called utility body 1 provided at its forward end with the driverscab 2 and having rearwardly extending side walls 3, 4, disposed inspaced parellel relation and including a series of built-in cabinets 5,6, '7, 8, for the storage of tools, small parts, and similar items ofequipment ordinarily used by repair crews. The side walls 3, 4, arespaced outwardly from each other and, together with the rear wall 9 ofthe cab compartment, define a cargo area a which is open at the top andrear. Mounted on the floor 10 adjacent to the crew compartment 2 is aconventional cable winch assembly 11 having a cable 12.

The floor 10 is extended rearwardly beyond the rear vertical faces ofthe side walls 3, 4, in the provision of an extension 13 provided on itsunder face with depending clevis-brackets 14 from which ground jacks 15are suspended. Welded upon the rear faces of the side walls 3, 4,adjacent the upper ends thereof, are horizontally aligned brackets 16and similarly welded on the upper faces of the side walls 3, 4,forwardly with respect to the brackets 16, are horizontally alignedauxiliary brackets 17. Swingably mounted on each bracket 17 by means ofa horizontal pivot pin 18 is a hydraulic ram or cylinder 19 having apiston rod 20 which is, in turn, provided at its forward end with aclevis 21.

V Swingably mounted on each bracket 16 by means of horizontal pivot pins22 are links 23 which are pivotally connected at their other ends bymeans of pivot pins 24 to the lower ends of derrick legs 25.

Also pivoted upon the pivot pins 24 are links 26 provided with clevises27 which, in turn, embrace the ends ofthe hydraulic cylinders 19 and arepivotally connected thereto by means of pivot pins 28 which are locatedforwardly of the pivot pins 18 (reference being made to Figure 1).

The clevises 21 of the piston rods 20 are pivotally mounted, by means ofpivot pins 29, in brackets 30 welded to the derrick legs 25 as shown inFigure 1. By reference to Figure 1, it will be noted that when thederrick is in transport position the pivot pin 24 is above, andrearwardly of, the pivot pin 22. Similarly, the pivot pin 18 is belowthe pivot pin 24, above the pivot pin 22, and forward of both such pivotpins. Furthermore, the pivot pin 28 is forward of, and above, the pivotpin 22, but below the pivot pin 18. It is this unique arrangement ofpivots that makes it possible for the derrick leg 25 to swing through anarc in excess of from the position shown in full lines to the positionshown in dotted lines in Figure 1. It also should be noted that thehydraulic cylinders 19 are of conventional construction and are,therefore, not described herein in specific detail. The hydrauliccylinders 19 are connected through conventional hand-operated shut-offvalves p and a main control valve V to a hydraulic system, substantiallyas shown in Figure 2. The valve V may be of any conventional internalconstruction and includes a control handle lz, so that each of the twocylinders 19, 19, will be operated simultaneously.

The derrick legs 25 are parallel with each other and with thelongitudinal axis of the body 1, and at their upper ends are rigidlyfastened into elbow fittings f which, in turn, connect with convergingtop-legs 31, the latter being operably connected at their outer endsinwardly toward each other by sheave block assembly 32 having guiderollers 33.

The portable derrick is ordinarily lowered to inoperative or horizontalposition as shown in Figure l and rests at its forward end in a somewhatL-shaped transport rack R rigidly carried on the forward wall of thetruck body 1 and extending upwardly and forwardly over the drivers cab2. in order to raise the derrick to the operative position shown inFigure 4, oil is admitted to the cylinders 19, pushing the piston rodsoutwardly and accordingly swinging the derrick upwardly and rearwardly.It will, of course, be understood that by manipulating the valve handleit different amounts of oil can be admitted to the cylinders 19, 19, sothat the derrick can be caused to assume virtually any position ofangulation within the maximum limits of travel permitted by thecomponent elements thereof. For example, the cylinders 19, 19, can beadjusted so that the sheave block assembly 32 is located more or lessvertically above the cargo area a in order that the cable 12 can bedropped vertically into the cargo area a for attachment to a heavyobject, such as the transformer switch box or the like, whereupon theheavy article can be lifted vertically up from the floor of the truckand suspended. Thereupon, by admitting further oil into the cylinders15%, 19, the sheave block assembly 32 can be swung rearwardly over andbeyond the rear end of the truck body 1, thereby transporting thesuspended heavy article rearwardly beyond the truck body into the clear,from which latter position it can be lowered to the ground or raised upto pole-height. When a heavy object such as a transformer is beinglifted by the cable 12, the derrick A may be locked in the particularposition to which it has been adjusted by closing the I hand shut-01fvalves 12.

it is also possible to provide a modified form of portable derrick ofthe type shown in Figure 7 for use with a truck body 1 having spacedparallel side walls 3', 4'. This modified form of derrick issubstantially similar to the previously described portable derrick,which comprises two converging derrick legs connected at their upperends by a sheave block assembly 3.2 having guide rollers 33, whichelements are substantially similar to the previously described derricklegs 25, sheave block assembly 32, and guide rollers 33. The derricklegs 25 are similarly mounted at their lower ends, by means of pivotpins 24, upon links 23, which are, in turn, pivoted upon brackets 16 bymeans of pivot pins 22.

Welded upon the side walls 3', 4, of the body 1' are brackets 34 whichare cross-connected by a bar 35. Similarly, the derrick legs 25 arerigidly cross-connected by horizontal bar 36 which is located just belowthe elbow fitting j" and the pivot pins 24 are endwise connected by ahorizontal bar 37. Pivotally connected between the midpoints of the bars35, 36, is a single hydraulic ram or cylinder 33 and similarly mountedon the bar 37 is a link 26' integrally provided at its forward end witha clevis 27 which straddles the lower end of the hydraulic cylinder 38and is pivotally connected to the bar 35.

This modified form of portable derrick functions in exactly the samemanner as the previously described structure and differs therefrom onlyin the utilization of the single hydraulic ram or cylinder 38. It will,of course, be understood in this connection that this modiried type ofportable derrick must either be employed for lighter types of work orthe single hydraulic cylinder 38 and the bars 35, 36, 37, must be ofsubstantial size and strength. It will also be apparent that in the caseof certain types of truck bodies the presence of the transverselyextending bars 35, 36, 37, would impede the cargo area and work spacewithin the truck body and, for such situations, it would be necessary touse a two ram boom rather than a single ram boom. These, of course, arematters of choice and selection which fall within the scope of thepresent invention.

Finally, it is also possible to provide a single legged one ram derrickembodying the present invention as shown in Figure 8. This derrickcomprises a single derrick leg 25" which is provided at its outer'endwith a sheave block assembly 32" and at its lower end is pivotallymounted on a link 23" by means of a pivot pin 24". The link 23" is, inturn, pivotally mounted, by means of a pivot pin 22", in a bracket 16".The elements are substantially similar to the previously describedelements 23, 24, 22, and 16, respectively. The pivot pin 24" alsoengages a link 26" having a clevis 27" which straddles the lower end of,and is pivotally connected to, a hydraulic cylinder 19", the latterbeing, in turn, pivotally connected upon a bracket 17". The hydrauliccylinder 19" is operatively provided with a piston rod 20 which ispivotally secured at its outer end to the derrick leg 25" by means of apivot pin 29" which is mounted in a bracket 30". This one legged singleram derrick also functions in substantially the same manner as thepreviously described two legged derricks.

It should'be understood that changes and modifications in the form,construction, arrangement, and combination of the several parts of theportable derrick may be made and substituted for those herein shown anddescribed without departing from the nature and principle of myinvention.

I claim:

1. A derrick comprising an approximately horizontal base, a boompivotally mounted at its lower end upon a pair of divergent links, oneof which is in turn pivotally mounted at its lower end upon the base,whereby the boom may be swung into various positions and being adapted,when in one extreme position, to extend forwardly over the base, andhydraulic cylinder means pivotally connected at its upper end to theboom outwardly therealong with respect to point of pivotal connectionbetween the boom and the link, said hydraulic cylinder means extendingdownwardly along the boom and having its lower end pivotally mounted onthe base at a point forwardly from the lower end of the boom when theboom is in said extreme position, the other link being pivotallyconnected at its lower end to the lower end of the hydraulic cylindermeans forwardly of the point of pivotal connection between saidhydraulic cylinder means and the base so that said lower end of the boomwill move along an arc upwardly and around the point of pivotalconnection between the hydraulic cylinder means and the base.

2. A derrick comprising a base, a boom pivotally mounted at its lowerend upon a pair of divergent links, one of which is in turn pivotallymounted at its lower end upon the base, whereby the boom may be swunginto various positions and being adapted, when in one extreme position,to extend forwardly over the base, and hydraulic cylinder meanspivotally connected at its upper end to the boom outwardly therealongwith respect to point of pivotal connection between the boom and thelinks, said hydraulic cylinder means extending downwardly along the boomand having its lower end pivotally mounted on the base forwardly fromthe lower end of the boom when the boom is in said extreme position, theother link being pivotally connected at its lower end to the lower endof the hydraulic cylinder means forwardly of the point of pivotalconnection between said hydraulic cylinder means and the base, saidother link extending forwardly and downwardly from the lower end of theboom so that said lower end of the boom will move along an arc upwardlyand around the point of pivotal connection between the hydrauliccylinder means and the base.

3. A derrick comprising a base, first pivot means mounted on the base,second pivot means also mounted on the base in spaced relation to thefirst pivot means, first link means rockably mounted on the second pivotmeans and extending upwardly therefrom, a boom pivotally mounted at itslower end upon the first link means for swinging movement into variouspositions and being adapted, when in one extreme position, to extendforwardly over the base, hydraulic cylinder means pivotally connected atits upper end to the boom outwardly therealong with respect to point ofpivotal connection between the boom and the first link means, saidhydraulic cylinder means extending downwardly along the boom and beingrockably mounted at its lower end upon the first pivot means, and secondlink means pivotally connected to the boom forwardly of the point ofpivotal connection between the boom and first pivot means, said secondlink means extending upwardly and being rockably connected to the lowerend of the boom so that said lower end of the boom will move along anarc upwardly and around the point of pivotal connection between thehydraulic cylinder and the first pivot means.

4. A derrick comprising a base, first pivot means mounted on the base,second pivot means also mounted on the base rearwardly in relation tothe first pivot means, first link means rockably mounted on the secondpivot means and extending upwardly therefrom, a boom pivotally mountedat its lower end upon the first link means for swinging movement intovarious positions and being adapted, when in one extreme position, toextend forwardly over the base, hydraulic cylinder means pivotallyconnected at its upper end to the boom outwardly therealong with respectto point of pivotal connection between the boom and the first linkmeans, said hydraulic cylinder means extending downwardly along the boomand being rockably mounted at its lower end upon the first pivot means,and clevis means pivotally connected to the boom forwardly of the pointof pivotal connection between the boom and first pivot means, saidclevis means extending upwardly and being rockably connected to thelower end of the boom so that said lower end of the boom will move alongan arc upwardly and around the point of pivotal connection between thehydraulic cylinder and the first pivot means.

5. A derrick comprising a base, first pivot means mounted on the base,second pivot means also mounted on the base rearwardly in relation tothe first pivot means, first link means rockably mounted on the secondpivot means and extending upwardly therefrom, a boom pivotally mountedat its lower end upon the first link means for swinging movement intovarious positions and being adapted, when in one extreme position, toextend forwardly over the base, hydraulic cylinder means pivotallyconnected at its upper end to the boom outwardly there- 'along withrespect to point of pivotal connection between the boom and the firstlink means, said hydraulic cylinder means extending downwardly along theboom and being rockably mounted at its lower end upon the first pivotmeans, and second link means pivotally connected to the boom forwardlyof the point of pivotal connection between the boom and first pivotmeans, said second link means extending upwardly and being rockablyconnected to the lower end of the boom around the point of pivotalconnection between the boom and the first link means so that said lowerend of the boom will move along an are upwardly and around the point ofpivotal connection between the hydraulic cylinder and the first pivotmeans.

6. A derrick comprising a base, a pair of laterally aligned first pivotsmounted on the base, a pair of laterally aligned second pivots alsomounted on the base rearwardly of the first pivots, a first linkrockably mounted on, and extending upwardly from, each of the secondpivots, a boom having two converging legs connected at their upper endsfor operatively supporting a sheave, said legs each respectively beingpivotally mounted at its lower end upon one of the first links forswinging movement into various positions, whereby said boom, when in oneextreme position, will extend forwardly over the base, a hydrauliccylinder pivotally connected at its upper end to each leg outwardlytherealong with respect to point of pivotal connection between such legand the first link, each of said hydraulic cylinders respectivelyextending downwardly along the leg with which it is associated and beingpivotally connected to one of the first pivots forwardly of the point ofpivotal connection betweeen such leg and the first link, and secondlinks pivotally connected to the cylinder forwardly of the point ofpivotal connection between such cylinder and the first pivot, saidsecond link extending rearwardly and being pivotally connected to thelower end of the leg and to the first link by a common pivot so thatsaid lower end of such legs will move along an arc upwardly and aroundfirst pivots.

7. A derrick comprising a base, a pair of laterally aligned first pivotsmounted on the base, a pair of laterally aligned second pivots alsomounted on the base rearwardly of the first pivots, a first linkrockably mounted on, and extending upwardly from, each of the secondpivots, a boom having two converging legs connected at their upper endsfor operatively supporting a sheave, said legs each respectively beingpivotally mounted at its lower end upon one of the first links forswinging movement into various positions, whereby said boom, when in oneextreme position, will extend forwardly over the base, a hydrauliccylinder pivotally connected at its upper end to each leg outwardlytherealong with respect to point of pivotal connection between such legand the first link, each of said hydraulic cylinders respectivelyextending downwardly along the leg with which it is associated and beingpivotally connected to one of the first pivots forwardly of the point ofpivotal connection between such leg and the first link, and second linkspivotally connected to the cylinder forwardly of the point of pivotalconnection between such cylinder and the first pivot, said second linkextending upwardly and rearwardly to converge with the first link andbeing pivotally connected to the lower end of the leg and to the firstlink by a common pivot so that said lower end of such legs will movealong an arc upwardly and around first pivots.

8. A derrick comprising a base, a pair of laterally aligned first pivotsmounted on the base, a pair of laterally aligned second pivots alsomounted on the base rearwardly of the first pivots, a first linkrockably mounted on, and extending upwardly from, each of the secondpivots, a boom having two converging legs connected at their upper endsfor operatively supporting a sheave, said legs each respectively beingpivotally mounted at its lower end upon one of the first links forswinging movement into various positions, whereby said boom, when in oneextreme position, will ext-end forwardly over the base, a hydrauliccylinder pivotally connected at its upper end to each leg outwardlytherealong with respect to point of pivotal connection between such legand the first link, each of said hydraulic cylinders respectivelyextending downwardly along the leg with which it is associated and beingpivotally connected to one of the first pivots forwardly of the point ofpivotal connection between such leg and the first link, and clevisespivotally connected to the cylinder forwardly of the point of pivotalconnection between such cylinder and the first pivot, said clevises 7extending rearwardly and being pivotally connected to the lower end ofthe leg and to the first link by a common pivot so that said lower endof such legs will move along an arc upwardly and around first pivots.

9. A derrick comprising a base, a pair of laterally aligned first pivotsmounted on the base, a pair of laterally aligned second pivots alsomounted on the base rearwardly of the first pivots, and having itspivot-center below the pivot-center of the first pivot, 21 first linkrockably mounted on, and extending upwardly from, each of the secondpivots, a boom having two converging legs connected at their upper endsfor operatively supporting a sheave, said legs each respectively beingpivotally mounted at its lower end upon one of the first links forswinging movement into various positions, whereby said boom, when in oneextreme position, will extend forwardly over the base, a hydrauliccylinder pivotally connected at its upper end to each leg outwardlytherealong with respect to point of pivotal connection between such legand the first link, each of said hydraulic cylinders respectivelyextending downwardly along the leg with which it is associated and beingpivotally connected to one of the first pivots forwardly of the point ofpivotal connection between such leg and the first link, and second linkspivotally connected to the cylinder forwardly of the point of pivotalconnection between such cylinder and the first pivot, said second linkextending rearwardly and being pivotally connected to the lower end ofthe leg and to the first link by a common pivot so that said lower endof such legs will move along an arc upwardly and around first pivots. I

10. A derrick comprising a base, a pair of laterally aligned firstpivots mounted on the base, a pair of laterally aligned second pivotsalso mounted on the base rearwardly of the first pivots, said secondpivots being located below the first pivots, a first link rockablymounted on, and extending upwardly from, each of the second pivots, aboom having two converging legs connected at their upper ends foroperatively supporting a sheave, said legs each respectively beingpivotally mounted at its lower end upon one of the first links forswinging movement into various positions, whereby said boom, when in oneextreme position, will extend forwardly over the base, a hydrauliccylinder pivotally connected at its upper end to each leg outwardlytherealong with respect to point of pivotal connection between such legand the first link, each of saidhydraulic cylinders respectivelyextending downwardly along the leg with which it is associated and beingpivotally connected to one of the first pivots forwardly of the point ofpivotal connection between such leg and the first link, and second linkspivotally connected to the cylinder forwardly of the point of pivotalconnection between such cylinder and the first pivot, said second linkextending rearwardly and being pivotally connected to the lower end ofthe leg and to the first link by a common pivot so that said lower endof such legs will move along an arc upwardly and around first pivots.

ll. A derrick comprising a base, a pair of laterally aiigned supportmembers mounted on the base, a pair of laterally aligned pivots alsomounted on the base rearwnrdly or the support means, a first cross-barmounted at its ends in and extending between the support members, firstlinks pivotally mounted at their lower ends respectively upon thepivots, a boom having two converging legs connected at their upper endsfor operatively supporting sheave, said legs each being respectivelypivotally mounted at its lower end upon one of the links for swingingmovement into various positions, whereby said boom, when in one extremeposition, will extend over the base, a second cross-bar extending iorwatransversely between said legs outwardly therealong with respect topoint of pivotal connection between the legs and the first links,hydraulic cylinder means pivotally connected at its lower end to saidfirst cross-bar, said hydraulic cylinder means extending between thelegs and having its lower end pivotally connected to the secondcross-bar, each leg being provided with a second link pivotallyconnected thereto at the point of pivotal connection between such legand the first links, and a third cross-bar extending transverselybetween said second links and being pivotally connected to the hydrauliccylinder means above the lower end thereof so that said lower end of thehydraulic cylinder means will move along an arc upwardly and around thepoints of pivotal connection between the first links and the base.

12. A derrick comprising a base, a pair of laterally aligned supportmembers mounted on the base, a pair of laterally aligned pivots alsomounted on the base downwardly and rearwardly of the support means, afirst crossbar mounted at its ends in and extending between the supportmembers, first links pivotally mounted at their lower ends respectivelyupon the pivots, a boom having two converging legs connected at theirupper ends for operatively supporting a sheave, said legs each beingrespectively pivotally mounted at its lower end upon one of the linksfor swinging movement into various positions, whereby said boom, when inone extreme position, will extend forwardly over the base, a secondcrossbar extending transversely between said legs outwardly therealongwith respect to point of pivotal connection between the legs and thefirst links, hydraulic cylinder means pivotally connected at its lowerend to said first crossbar, said hydraulic cylinder means extendingbetween the legs and having its lower end pivotally connected to thesecond cross-bar, each leg being provided with a second link pivotallyconnected thereto at the point of pivotal connection between such legand the first links, and a third cross-bar extending transverselybetween said second links and being pivotally connected to the hydrauliccylinder means above the lower end thereof so that said lower end of thehydraulic cylinder means will move along an arc upwardly and around thepoints of pivotal connection between the first links and the base.

13-. A derrick comprising a base, a pair of laterally aligned supportmembers mounted on the base, a pair of laterally aligned pivots alsomounted on the base rearwardly of the support means, a first cross-barmounted at its ends in and extending between the support members, firstlinks pivotally mounted at their lower ends respectively upon thepivots, a boom having two converging legs connected at their upper endsfor operatively supporting a sheave, said legs each being respectivelypivotally mounted at its lower end upon one of the links above the firstcross-bar for swinging movement into various positions, whereby saidboom when in one extreme position, will extend forwardly over the base,a second cross-bar extending transversely between said legs outwardlytherealong with respect to point of pivotal connection between the legsand the first links, hydraulic cylinder means pivotally connected at itslower end to said first cross-bar, said hydraulic cylinder meansextending between the legs and having its lower end pivotally connectedto the second cross-bar, each leg being provided with a second linkpivotally connected thereto at the point of pivotal connection betweensuch leg and the first links, and a third cross-bar extendingtransversely between said second links and being pivotally connected tothe hydraulic cylinder means above the lower end thereof so that saidlower end of the hydraulic cylinder means will move along an arcupwardly and around the points of pivotal connection between the firstlinks and the base.

14. A derrick comprising a base, a first link pivotally mounted on, andextending upwardly from, the base, a single-leg boom pivotally mountedat its lower end upon the upper end of the first link for swingingmovement into various positions and being adapted, when in one extremeposition, to extend forwardly over the base, hydraulic cylinder meanspivotally connected at its upper end to the boom outwardly therealongwith respect to point of pivotal connection between the boom and thefirst link, said hydraulic cylinder means extending downwardly along theboom and being pivotally connected at its lower end to the baseforwardly with respect to the lower end of the boom when the boom is insaid extreme position, and a second link pivotally connected to the boomat the point of pivotal connection between the boom and the first link,said second link being pivotally connected to the hydraulic cylindermeans forwardly of the point of pivotal connection between the hydrauliccylinder means and the base, said links, furthermore, being pivoted tothe boom and base respectively on opposite sides of the point at whichthe boom is pivoted to the base, said first and second links extendingforwardly and being pivotally connected to each other and to the lowerend of the hydraulic cylinder means so that said lower end of thehydraulic cylinder means will move along an arc upwardly and around thepoint of pivotal connection between the boom and the base.

15. A derrick comprising a base, a first link pivotally mounted on, andextending upwardly from, the base, a single-leg boom pivotally mountedat its lower end upon the upper end of the first link for swingingmovement into various positions and being adapted, when in one extremeposition, to extend forwardly over the base, hydraulic cylinder meanspivotally connected at its upper end to the boom outwardly therealongwith respect to point of pivotal connection between the boom and thefirst link, said hydraulic cylinder means extending downwardly along theboom and being pivotally connected at its lower end to the baseforwardly with respect to the lower end of the boom when the boom is insaid extreme position, and a second link pivotally connected to the boomat the point of pivotal connection between the boom and the first link,said second link being pivotally connected to the hydraulic cylindermeans forwardly of the point of pivotal connection between the hydrauliccylinder means and the base and below the point at which the first linkis pivoted to the boom, said links, furthermore, being pivoted to theboom and base respectively on opposite sides of the point at which theboom is pivoted to the base, said first and second links extendingforwardly and being pivotally connected to each other and to the lowerend of the hydraulic cylinder means so that said lower end of thehydraulic cylinder means will move along an arc upwardly and around thepoint of pivotal connection between the boom and the base.

16. A derrick comprising a base, pivot means mounted on the base, linkmeans rockably mounted on the pivot means, a boom pivotally mounted atits lower end upon the link means, hydraulic cylinder means pivotallymounted at its upper end to the boom and at its lower end to the base,and means operatively connecting said link to the base-pivoted end ofthe hydraulic cylinder means for swinging the link away from the basearound the point at which the link is pivoted to the base so as toproduce movement between the pivotal connection of the link and thelower end of the boom responsive to swing ing movement of thebase-pivoted end of the hydraulic cylinder means.

17. A derrick comprising a base, pivot means mounted on the base, linkmeans swingably mounted on the pivot means, a boom swingably mounted atits lower end upon the link means for swinging movement into variouspositions and being adapted when in one extreme position to extendforwardly over the base, hydraulic cylinder means pivotally connected atits upper end to the boom outwardly therealong with respect to the pointof pivotal connection between the boom and said link means, saidhydraulic cylinder means extending downwardly along the boom and havingits lower end spaced forwardly from the lower end of the boom when theboom is in said extreme position, said hydraulic cylinder means beingpivotally connected to the base at such lower end, and means operativelyconnecting said link and the lower end of the hydraulic cylinder meansso that as the boom and hydraulic cylinder means swing upwardly fromsaid extreme position the link will also be swung around the point atwhich said link is pivoted to the base so as to produce correspondingmovement of the pivotal connection between the link and the lower end ofthe boom.

18. A derrick comprising a base, a link pivotally mounted at its lowerend upon the base, a boom pivotally connected at its lower end to thelink for swinging movement into various positions and being adapted whenin one extreme position to extend forwardly over the base, hydrauliccylinder means pivotally connected at its upper end to the boomoutwardly therealong with respect to point of pivotal connection betweenthe boom and the link, said hydraulic cylinder means extendingdownwardly along the boom and having its lower end pivotally mounted onthe base forwardly from the lower end of the boom when the boom is insaid extreme position, a connecting element mounted adjacent to thelower end of the hydraulic cylinder means and also being operativelyconnected to the link whereby to cause said link to rotate about itspivotal connection with the base as the boom swings out of said extremeposition and away from the base so that the point of pivotal connectionbetween the lower end of the boom and said link will move away from thebase responsive to movement of the hydraulic cylinder means.

19. A derrick comprising a base, a link pivotally mounted on the base, aboom pivotally mounted at its lower end upon the link for swingingmovement into various positions and being adapted when in one extremeposition to extend forwardly over the base, hydraulic cylinder meanspivotally connected at its upper end to the boom outwardly therealongwith respect to point of pivotal connection between the boom and thelink, said hydraulic cylinder means extending downwardly along the boomand having its lower end pivotally connected to the base forwardly fromthe lower end of the boom when the boom is in said extreme position, aconnecting element mounted on the lower end of the hydraulic cylindermeans, and means operatively associated with said connecting element andthe link whereby to cause said link to rotate about its pivotalconnection with the base as the boom swings out of said extreme positionand away from the base so that the point of pivotal connection betweenthe lower end of the boom and said link will move away from the base inthe same direction as the boom.

No references cited.

